Field of the Invention
The present invention relates to image forming apparatuses and cartridges used for the image forming apparatuses. The present invention can be particularly used for an electrophotographic copier, a printer, (such as a light-emitting diode (LED) printer or a laser beam printer), a facsimile machine, a word processor, and so forth.
Description of the Related Art
In an electrophotographic image forming apparatus, an electrophotographic photosensitive member serving as an image bearing member that typically has a drum shape, that is, a photosensitive drum is uniformly charged. Next, by selectively exposing the charged photosensitive drum to light, an electrostatic latent image (electrostatic image) is formed on the photosensitive drum. The electrostatic latent image formed on the photosensitive drum is subsequently developed into a toner image with toner as developer. The toner image formed on the photosensitive drum is transferred onto a recording medium such as recording paper or a plastic sheet. Then, by applying heat and pressure to the toner image transferred onto the recording medium, the toner image is fixed onto the recording medium. Thus, the image is recorded.
In general, maintenance including toner supply and maintenance of a variety of process devices is required for such an image forming apparatus. In order to facilitate the toner supply and the maintenance of the process devices, a process cartridge that is detachably attachable to a main body of the image forming apparatus has come into practical use. In this process cartridge, a photosensitive drum, a charging device, a developing device, a cleaning device, and so forth are gathered together in a frame so as to be provided as a cartridge.
Since maintenance of the apparatus can be performed by a user himself or herself with this process cartridge method, operability can be significantly improved, and the image forming apparatus with good usability can be provided. Thus, this process cartridge method is widely used for the image forming apparatus.
Furthermore, in order to receive a rotational drive force from the image forming apparatus main body in the above-described cartridge, the following structure described in Japanese Patent Laid-Open No. 2010-140051 is known. That is, a main-body-side engagement member provided with a rotational force applying portion at a distal end of a drive shaft that transmits a drive force of a motor is provided on an image forming apparatus main body (main body) side. In contrast, an inclinable coupling is provided at one end of a photosensitive drum in the longitudinal direction on a process cartridge side.
This coupling includes a rotational force receiving portion and a rotational force transmitting portion. The rotational force receiving portion is brought into engagement with the main-body-side engagement member so as to receive the drive force from the rotational force applying portion. The rotational force transmitting portion transmits the drive force received by the rotational force receiving portion to the photosensitive drum. The coupling is inclined so that the coupling can assume a first orientation and a second orientation. In the first orientation, rotational drive is transmitted from the main-body-side engagement member that is in engagement in a state substantially parallel to a rotational axis of the photosensitive drum. In the second orientation, engagement with the main-body-side engagement member is released.
Thus, the coupling assumes the second orientation when the process cartridge that is detachably attachable in a direction substantially perpendicular to the rotational axis direction of the main-body-side engagement member is attached or detached. In the second orientation, the coupling is inclined such that a distal end side of the coupling is moved further in a process cartridge attachment direction than a proximal end side of the coupling. Accordingly, the main-body-side engagement member and the coupling can be brought into engagement with each other so as to transmit the drive without a mechanism that moves the main-body-side engagement member in the rotational axis direction.
Nowadays, there is a demand for an increase in the capacity of a process cartridge. In order to realize this, however, the amount of toner is increased. This leads to an increase in the weight of the process cartridge. That is, a heavy process cartridge is attached to or detached from the image forming apparatus main body by the user. Here, in order to stably bring the above-described inclinable coupling into engagement with the main-body-side engagement member, the position of the coupling before the engagement needs to be stabilized. In particular, when the inclinable coupling is applied to the heavy process cartridge, a structure for attachment and detachment that allows the process cartridge to be more stably attached to and detached from the image forming apparatus is needed.